Tape printing apparatus of the general type with which the present invention is concerned are disclosed in EP-A-322918 and EP-A-322919 (Brother Kogyo Kabushiki Kaisha) and EP-A-0267890 (Varitronics). These printers each include a printing device having a cassette receiving bay for receiving a cassette or tape holding case. In EP-A-0267890, the tape holding case houses ink ribbon and a substrate tape, the latter comprising an upper image receiving layer secured to a backing layer by adhesive. In EP-A-322918 and EP-A-322919, the tape holding case houses an ink ribbon, a transparent image receiving tape and a double sided adhesive tape which is secured at one of its adhesive coated sides to the image tape after printing and which has a backing layer peelable from its other adhesive coated sides. The image is printed on the side of the image receiving tape which is adhered to the adhesive coated tape. Thus, the printed image is covered by a protective layer. With both of these apparatus, the image transfer medium, (ink ribbon) and image receiving tape (substrate) are in the same cassette.
The present applicants have developed a different type of printing apparatus which is described for example in European patent application No. 578372. In this printing apparatus, the substrate tape is similar to that described in EP-A-0267890 but is housed in its own tape holding case whilst the ink ribbon is similarly housed in its own tape holding case.
Reference is also made to JP-A-2204074 which discloses an ink cartridge having removable shafts holding an ink supply.
In all of these cases, the image receiving tape passes in overlap with the ink ribbon through a print zone consisting of a fixed print head and a platen against which the print head can be pressed to cause an image to transfer from the ink ribbon to the image receiving tape. There are many ways of doing this, including dry lettering or dry film impression, but the most usual way at present is by thermal printing where the print head is heated and the heat causes ink from the ink ribbon to be transferred to the image receiving tape.
As discussed above, all of the above mentioned apparatus use a fixed print head. This is disadvantageous when it is desired to print on labels having a relatively large width or where the same apparatus is designed to be used with a number of different widths of tape. In the first situation, the print head would need to be as wide as the maximum width of the tape. Thus with large widths of tape, the fixed print head would also have to be relatively large. Large print heads are relatively expensive and accordingly increase the cost of the apparatus. Additionally, with large print heads, the power required to activate the large number of printing elements on such a print head can be disadvantageous for battery operated arrangements. If the arrangement is mains powered the associated components can be costly. This is a particular problem where a large percentage of the printing elements on the print head are operated at the same time.
In the second situation discussed above, the print head would have to have the same size as the largest width of tape designed to be used with the tape printing apparatus. If such apparatus are only rarely used with the maximum width of tape, the associated additional cost of having a print head capable of printing on large widths of tapes would not be justified.
Accordingly such apparatus would be unnecessarily expensive or would not be arranged to have the flexibility to print on a wide range of different width tapes. The associated disadvantages with a large print head of cost would also be present with this second situation.
A further disadvantage of using a fixed print head is that multiple colour printing can be difficult to implement with a fixed print head as the image receiving tape would have to be moved back and forth past the print head. Alignment of the images in the different colours may be difficult to achieve reliably.